KR20180021171A - Seismic wave device, high frequency front end circuit and communication device - Google Patents

Abstract

Provided is a seismic wave device having a high Q value and little variation in characteristics depending on a film thickness variation of the piezoelectric film.
Wherein the bass sound film (4), the piezoelectric film (5), and the IDT electrode (6) are laminated in this order on a treble support substrate (3) as a high sound velocity member. The film thickness of the piezoelectric film 5 is more than 1.5? And not more than 3.5? When the wavelength of the elastic wave determined by the electrode finger period of the IDT electrode 6 is?. The bulk acoustic wave propagating through the treble support substrate 3 is higher in speed than the acoustic wave propagating through the piezoelectric film 5. The sound velocity of the bulk wave propagating through the bass sound insulation film 4 is lower than that of the acoustic wave propagating through the piezoelectric film 5.

Description

Seismic wave device, high frequency front end circuit and communication device

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an acoustic wave device used in a resonator, a band filter, and the like, and a high-frequency front end circuit and a communication device using the same.

Conventionally, as a resonator or a bandpass filter, an acoustic wave device has been widely used. The following Patent Document 1 discloses an elastic wave device in which a low sound attenuation film, a piezoelectric film and an IDT electrode are laminated in this order on a high-sound speed supporting substrate. Patent Document 1 discloses an acoustic wave device in which a high-sound-attenuating film, a bass sound film, a piezoelectric film, and an IDT electrode are laminated in this order on a support substrate.

The sound velocity of the bulk wave propagating through the treble support substrate or the high sound velocity film is higher than that of the acoustic wave propagating through the piezoelectric film. The bulk wave velocity propagating through the bass membrane is slower than the acoustic wave velocity propagating through the piezoelectric film.

WO2012 / 086639A1

In the elastic wave device described in Patent Document 1, the Q value can be improved by using a laminate of a high-sound-speed supporting substrate and a low-sound-absorbing film or a laminate of a high sound-insulating film and a low sound-absorbing film. However, the film thickness of the piezoelectric film used was considerably thin at 1.5? Or less. For this reason, there has been a problem that the variation in characteristics due to the film thickness deviation of the piezoelectric film becomes large.

An object of the present invention is to provide an elastic wave device, a high-frequency front end circuit, and a communication device, which have a high Q value and little variation in characteristics in accordance with a film thickness variation of the piezoelectric film.

An acoustic wave device according to the present invention is an acoustic wave device having a piezoelectric film, comprising: a treble component having a sound velocity of a bulk wave propagating faster than an acoustic wave propagating through the piezoelectric film; and a high sound velocity member laminated on the treble component, And an IDT electrode formed on one surface of the piezoelectric film, wherein the thickness of the piezoelectric film is at least one of a thickness of the piezoelectric film and a thickness of the piezoelectric film And the wavelength of the elastic wave determined by the electrode finger period of the IDT electrode is?, The wavelength is more than 1.5? And not more than 3.5?.

In a specific aspect of the acoustic wave device according to the present invention, the treble member is a treble support substrate. In this case, the structure can be simplified and the number of parts can be reduced.

In a specific aspect of the acoustic wave device according to the present invention, the acoustic wave device further includes a bonding layer provided at the position from the high-sound-speed supporting substrate to the interface between the bass sound film and the piezoelectric film.

In a specific aspect of the acoustic wave device according to the present invention, the bonding layer is formed on the interface between the high-sound-speed supporting substrate and the low-sound-attenuating film, or between the low-sounding attenuating film and the piezoelectric film And is present at any one position within the interface with the substrate.

In another specific aspect of the acoustic wave device according to the present invention, the treble support substrate is a silicon substrate. In this case, since the silicon substrate has excellent processability, the acoustic wave device can be easily manufactured. Further, the deviation of the characteristics can be further reduced. Further, it is possible to suppress the higher order mode.

In another specific aspect of the acoustic wave device according to the present invention, the acoustic wave device further includes a support substrate, and the treble member is a treble film provided on the support substrate.

In another specific aspect of the acoustic wave device according to the present invention, the acoustic wave device further includes a bonding layer provided at any one position from the high-sound-insulating film to the interface between the bare sound film and the piezoelectric film.

In another specific aspect of the acoustic wave device according to the present invention, the bonding layer is formed on the interface between the high-sound-insulating inner film and the low sound-absorbing film, between the bare inner film and the piezoelectric film It exists in either position.

In another specific aspect of the acoustic wave device according to the present invention, the bonding layer includes a metal oxide layer or a metal co-ordinate layer.

In another specific aspect of the acoustic wave device according to the present invention, the bonding layer includes a Ti layer, and the thickness of the Ti layer is 0.4 nm or more and 2.0 nm or less.

In another specific aspect of the acoustic wave device according to the present invention, the film thickness of the Ti layer is 0.4 nm or more and 1.2 nm or less.

In another specific aspect of the acoustic wave device according to the present invention, the bass sound film is composed of silicon oxide or a film containing silicon oxide as a main component. In this case, the frequency temperature characteristic can be improved.

In another specific aspect of the acoustic wave device according to the present invention, the piezoelectric film is made of LiTaO ₃ . In this case, it is possible to provide a seismic wave device having a higher Q value.

In another specific aspect of the acoustic wave device according to the present invention, the bass sound film is made of silicon oxide, the bonding layer is present in the bass sound film, and the bass sound film is formed on the piezoelectric film side And a second bass film layer located on the side opposite to the piezoelectric film of the bonding layer, wherein when the wavelength of the acoustic wave used by the acoustic wave device is lambda, 1 has a film thickness of 0.12? Or more.

In another specific aspect of the acoustic wave device according to the present invention, the first bass sound film layer has a thickness of 0.22 lambda or more.

In another specific aspect of the acoustic wave device according to the present invention, an intermediate layer disposed between the treble mechnism and the support substrate is further included.

A high-frequency front-end circuit according to the present invention includes an acoustic wave device constructed according to the present invention and a power amplifier.

The communication apparatus according to the present invention includes the high-frequency front end circuit, the RF signal processing circuit, and the baseband signal processing circuit.

In the acoustic wave device according to the present invention, since the Q value is high and the film thickness of the piezoelectric film is more than 1.5? And not more than 3.5 ?, the variation in characteristics due to the film thickness deviation is unlikely to occur.

1 (a) and 1 (b) are a schematic front sectional view and a schematic plan view showing an electrode structure of an acoustic wave device according to a first embodiment of the present invention.
2 is a view showing the relationship between the film thickness and the Q of the LiTaO ₃ film in the acoustic wave device.
3 is a graph showing the relationship between the film thickness of the LiTaO ₃ film in the acoustic wave device and the frequency temperature coefficient TCF.
4 is a diagram showing the relationship between the film thickness of the LiTaO ₃ film in the acoustic wave device and the sound velocity.
5 is a schematic front sectional view of an acoustic wave device according to a second embodiment of the present invention.
6 is a diagram showing the relationship between the film thickness of the high-sound-attenuating film and the energy concentration in the acoustic wave device.
7 is a schematic front sectional view of an acoustic wave device according to a third embodiment of the present invention.
8 is a diagram showing impedance characteristics of the acoustic wave device of the third embodiment and the conventional example.
9 is a schematic front sectional view of an elastic wave device according to a fourth embodiment of the present invention.
10 is a schematic front sectional view of an acoustic wave device according to a fifth embodiment of the present invention.
11 is a schematic front sectional view of an elastic wave device according to a sixth embodiment of the present invention.
12 is a schematic front sectional view of an acoustic wave device according to a seventh embodiment of the present invention.
13 is a schematic front sectional view of an acoustic wave device according to an eighth embodiment of the present invention.
14 is a diagram showing the relationship between the film thickness of the SiO ₂ film and the Q value.
15 is a diagram showing the relationship between the film thickness of the Ti layer and the Q value.
16 is a configuration diagram of a high-frequency front-end circuit.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, with reference to the drawings, the present invention will be clarified by describing specific embodiments thereof.

Further, it is pointed out that each embodiment described in this specification is illustrative, and that partial substitution or combination of constitution is possible among other embodiments.

1 (a) is a schematic front cross-sectional view of an acoustic wave device as a first embodiment of the present invention.

The elastic wave device (1) has a high-sound speed supporting substrate (3) as a high sound velocity member. On the high-sound-speed support substrate 3, a low-sound-absorbing film 4 having a relatively low sound velocity is laminated. In addition, the piezoelectric film 5 is laminated on the low-sound-performance film 4. An IDT electrode 6 is laminated on the upper surface (upper surface) of the piezoelectric film 5. [ Alternatively, the IDT electrode 6 may be laminated on the lower surface of the piezoelectric film 5.

Since the bass sound film 4 is disposed between the high sound velocity member and the piezoelectric film 5, the sound velocity of the acoustic wave is lowered. The energy of the elastic waves is concentrated in a medium which is essentially low in sound. Therefore, it is possible to enhance the effect of keeping the energy of the elastic wave in the piezoelectric film 5 and the IDT electrode 6 excited by the acoustic wave. Therefore, according to the present embodiment, the loss can be reduced and the Q value can be increased as compared with the case where the low-sound-after-production film 4 is not provided.

The high-sound-speed supporting substrate 3 functions to prevent an acoustic wave from leaking to a structure lower than the high-sound-speed supporting substrate 3 while retaining the acoustic wave in a portion where the piezoelectric film 5 and the low sound insulating film 4 are laminated have. That is, the energy of the acoustic waves of the specific mode used for obtaining the characteristics of the filter or the resonator is distributed over the entirety of the piezoelectric film and the low sound film, distributed to a part of the high sound quality support substrate 3 on the side of the low sound film 4, It is not distributed under the high sound velocity member. The mechanisms for holding the acoustic waves by the treble support substrate 3 are the same mechanisms as those of the surface waves of the SH wave and the non-leaky LO waves. For example, in the document entitled " Introduction of surface acoustic wave device simulation technology ", Hashimoto Kenya, Realite, P90-P91. This mechanism is different from the clogging mechanism using Bragg reflectors by acoustic multi-layer films.

The high-sound-speed support substrate 3 can be made of a suitable material that satisfies the sound velocity relationship described later. As such a material, a dielectric such as various ceramics such as sapphire, alumina, magnesia, silicon nitride, aluminum nitride, silicon carbide, corederite, mullite, stearate or posterior, or a semiconductor such as silicon or gallium nitride or a resin substrate Can be used. In this embodiment, the treble support substrate 3 is made of silicon.

The high-sound-speed supporting substrate 3 functions to prevent the surface acoustic waves from leaking to the structure below the high-sound-speed supporting substrate 3, while retaining the surface acoustic wave in a portion where the piezoelectric film 5 and the low sound insulating film 4 are laminated . In order to confine the surface acoustic wave to the portion where the piezoelectric film 5 and the bass sound insulation film 4 are laminated, the thickness of the high sound quality support substrate 3 is preferably thicker.

In the present specification, the high sound velocity member refers to a member in which the sound velocity of a bulk wave in the high sound velocity member becomes higher than a sound velocity of an acoustic wave such as a surface wave or a boundary wave propagating through a piezoelectric film. Further, the low-sound-level film refers to a film in which the sound velocity of a bulk wave propagating through the low sound-level film becomes lower than that of an acoustic wave propagating through the piezoelectric film. In addition, elastic waves having different acoustic velocities are excited from the IDT electrodes of any structure, but elastic waves propagating through the piezoelectric film exhibit acoustic waves of a specific mode used for obtaining properties of filters and resonators. The mode of the bulk wave for determining the acoustic velocity of the bulk wave is defined according to the mode of use of the acoustic wave propagating through the piezoelectric film. The case where the treble velocity member and the bass sound film are isotropic with respect to the propagation direction of the bulk wave is as shown in Table 1 below. That is, the above-mentioned treble and bass frequencies are determined by the mode of the bulk acoustic wave of the right axis of Table 1 with respect to the main mode of the acoustic wave of the left axis of Table 1 below. The P wave is the longitudinal wave and the S wave is the transverse wave.

In the following Table 1, U1 denotes a P wave as a main component, U2 denotes an SH wave as a main component, and U3 denotes an elastic wave having a SV wave as a main component.

Correspondence between the acoustic wave mode of the piezoelectric film and the bulk wave mode of the dielectric film (when the dielectric film is an isotropic material) Main mode of elastic wave propagating in piezoelectric film Mode of bulk wave propagating in dielectric film U1 P wave U2 S wave U3 + U1 S wave

In the case where the bass sound film 4 and the treble support substrate 3 are anisotropic in the propagation property of the bulk wave, as shown in Table 2 below, the mode of the bulk wave for determining the high sound quality and the low sound quality Is determined. Further, in the mode of the bulk wave, the later of the SH wave and the SV wave is called a later transverse wave, and the faster one is called a faster transverse wave. Which one is a transverse wave depends on the anisotropy of the material. In LiTaO ₃ and LiNbO ₃ near the rotational Y-cut, the transverse waves of the SV wave and the SH wave of the bulk wave become fast transverse waves.

Correspondence between the acoustic wave mode of the piezoelectric film and the bulk wave mode of the dielectric film (when the dielectric film is an anisotropic material) Main mode of elastic wave propagating in piezoelectric film Mode of bulk wave propagating in dielectric film U1 P wave U2 SH wave U3 + U1 SV wave

In the present embodiment, the bass sound film 4 is made of silicon oxide and the thickness thereof is not particularly limited. However, when the wavelength of the acoustic wave determined by the electrode finger period of the IDT electrode is? . By reducing the film thickness of the low-sound-attenuating film to 2.0 or less, it is possible to reduce the film stress, and as a result, it is possible to reduce warpage of the wafer, thereby improving the yield rate and stabilizing the characteristics.

As a material constituting the bass sound-absorbing film 4, a suitable material having a bulk wave sound velocity in a lower sound than an acoustic wave propagating through the piezoelectric film 5 can be used. As such a material, a medium composed mainly of the above-described materials such as silicon oxide, glass, silicon oxynitride, tantalum oxide, or a compound in which silicon oxide is doped with fluorine, carbon, or boron can be used.

As the material of the above-mentioned low-sound-absorbing film and high-sound-speed supporting substrate, a suitable material can be used as long as the above sound velocity relationship is satisfied.

The piezoelectric film 5 is, in the present embodiment, 50.0 ° Y-cut LiTaO of _3, that is formed of LiTaO ₃ with Euler angles (Euler angles) (0 °, 140.0 °, 0 °). The film thickness of the piezoelectric film 5 is in the range of more than 1.5? And not more than 3.5? When the wavelength of the surface acoustic wave determined by the electrode finger period of the IDT electrode 6 is?. In this embodiment, 2.0?. However, the piezoelectric film 5 may be made of another cut angle LiTaO ₃ , or may be made of a piezoelectric single crystal other than LiTaO ₃ . By using the piezoelectric single crystal, the loss of the material itself can be reduced, and the characteristics of the device can be improved.

The IDT electrode 6 is made of Al in the present embodiment. However, the IDT electrode 6 can be formed of a suitable metal material such as Al, Cu, Pt, Au, Ag, Ti, Ni, Cr, Mo, W or an alloy mainly composed of any of these metals . The IDT electrode 6 may have a structure in which a plurality of metal films made of these metals or alloys are laminated.

1 (a), an electrode structure shown in Fig. 1 (b) is formed on the piezoelectric film 5. The electrode structure shown in Fig. That is, the IDT electrode 6 and the reflectors 7 and 8 disposed on both sides of the IDT electrode 6 in the acoustic wave propagation direction are formed. Thereby, a one-port type elastic wave resonator is constituted. However, the electrode structure including the IDT electrode in the present invention is not particularly limited, and may be a ladder filter, a longitudinal coupling filter, a lattice filter, a transversal filter, It can be modified to construct a filter.

In the acoustic wave device 1, since the high-sound-speed supporting substrate 3, the low-sound-insulating film 4, and the piezoelectric film 5 are laminated, the Q value can be increased like the acoustic wave device described in Patent Document 1. Particularly, since the thickness of the piezoelectric film 5 is in the range of more than 1.5? And not more than 3.5?, Not only the Q value can be increased but also the characteristic of the piezoelectric film 5 The deviation can be suppressed. This will be described with reference to Figs. 2 to 4. Fig.

2 is a plan view of a sound insulating film 4 made of a SiO ₂ film having a thickness of 0.35 lambda and a piezoelectric thin film 4 made of LiTaO ₃ having an Euler angle (0 DEG, 140.0 DEG, 0 DEG) Film thickness of LiTaO ₃ in the elastic wave device in which the film 5 is laminated, and the Q value. The vertical axis in FIG. 2 is a product of the Q characteristic of the resonator and the specific band (? F), and is generally used as one index for judging whether the device characteristics are good or bad. 3 is a graph showing the relationship between the film thickness of LiTaO ₃ and the frequency temperature coefficient TCF. 4 is a graph showing the relationship between the film thickness of LiTaO ₃ and the sound velocity. As apparent from Fig. 2, when the film thickness of LiTaO ₃ is 3.5 or less, the Q value becomes higher and the Q characteristic becomes better than that when the film thickness exceeds 3.5 ?. More preferably, in order to increase the Q value, the thickness of LiTaO ₃ is preferably 2.5 or less.

Further, FIG. 3 shows that when the thickness of LiTaO ₃ is 2.5 了 or less, the absolute value of the frequency temperature coefficient TCF can be made smaller than that when the absolute value of the temperature coefficient TCF exceeds 2.5 了. More preferably, in the range of 2? Or less, the absolute value of the frequency temperature coefficient TCF can be set to -10 ppm / ° C or less, which is preferable.

As is also apparent from the 4, if the thickness of the LiTaO ₃ exceeds 1.5λ, it can be seen that the acoustic velocity of the change following the LiTaO ₃ film thickness change the least. Therefore, since the frequency dependence of LiTaO ₃ with respect to the film thickness is remarkably reduced, it is understood that the variation of the frequency-temperature characteristic with the film thickness change is considerably reduced.

In the acoustic wave device 1 of the present embodiment, the high-sound-speed support substrate 3 is made of silicon. In the high-sound speed support substrate 3 made of silicon, workability is good. Also, the high-order mode can be effectively suppressed.

Further, since the bass sound-absorbing film 4 is made of SiO ₂ , the absolute value of the frequency temperature coefficient TCF can also be reduced.

As the piezoelectric film 5, and the use of LiTaO _3, the thickness of the piezoelectric film 5 is in a range of the specified because, if andago not the thickness of the piezoelectric film 5 is constant, sufficient Q value And the variation of characteristics is small.

At least one layer of the adhesion layer, the lower film, the low sound velocity layer and the high sound velocity layer may be formed on at least one boundary of the piezoelectric film, the low acoustic sound film and the high sound speed support substrate.

Although the bass sound film 4, the piezoelectric film 5 and the IDT electrode 6 are stacked in this order on the high-sound-speed support substrate 3 in the above embodiment, the second implementation The high-sound-performance underlayer 3A may be laminated on the support substrate 2 as a high sound velocity member. As the support substrate 2 in this case, suitable materials such as silicon, alumina, lithium tantalate, lithium niobate, piezoelectric materials such as quartz, various ceramics such as zirconia, and dielectrics such as glass can be used.

Also in the second embodiment, since the film thickness of the piezoelectric film 5 is more than 1.5? And not more than 3.5? As in the first embodiment, the Q value is high and the film thickness of the piezoelectric film 5 It is possible to reduce the deviation of the characteristic according to the thickness deviation. The inventors of the present invention have confirmed that, in the first and second embodiments, the region where the Q characteristic is improved, the region where the TCF is improved, and the region where the frequency is stable are the same. Therefore, the results of Figs. 2 to 4 in the first embodiment are also suitable for the second embodiment.

In the second embodiment, the high sound attenuation film 3A has a function of holding the acoustic waves, and the mode of the main vibration is not leaked to the support substrate. That is, if the supporting substrate can support the film structure, it becomes possible to use any sonic material. That is, the degree of freedom of selection of the supporting substrate can be increased.

Although the bonding layer is used to form the acoustic wave devices of the first and second embodiments, in the case of the first embodiment, it is necessary to dispose the bonding layer in the area where the main mode is excited. Therefore, this causes a variation in characteristics. On the other hand, in the case of the second embodiment, the bonding layer can be disposed at a place where the main mode does not reach by disposing the bonding layer in the high-sound-insulating film or on the side of the support substrate. Therefore, the second embodiment is less susceptible to variations in characteristics.

The dielectric film may be sandwiched between the treble mechnism 3A and the support substrate 2. For example, by arranging the low sound film between the high-definition sound-deadening film 3A and the support substrate 2, it is possible to attract only unnecessary high-order modes to the support substrate side without changing the mode of the main vibration. Therefore, the suppression of the higher-order mode can be easily achieved in the second embodiment.

The high-sound-after-production film 3A has a function to confine surface acoustic waves to the piezoelectric film 5 and the low-sound-performance film 4, and the thickness of the high-sound-production film 3A is preferably as thick as possible. As shown in Fig. 6, the energy concentration at the resonance point (resonance point) can be made 100% by setting the film thickness of the high-sound-quality film made of the AlN film to 0.3λ or more. Further, by setting the value to 0.5 or larger, the energy concentration at the anti-resonance point can be made 100%, and better device characteristics can be obtained.

At least one layer of the adhesion layer, the lower film, the low sound velocity layer and the high sound velocity layer may be formed on at least one boundary of the piezoelectric film, the low acoustic sound film, the high sound insulating film and the support substrate.

Further, in the second embodiment, the dielectric film 9 is laminated so as to cover the IDT electrode 6. As the dielectric film 9, SiO ₂ , SiN, or the like can be used. Preferably, the SiO ₂ is used, in that case, it is possible to reduce more than the absolute value of frequency-temperature coefficient TCF. On the other hand, also in the first embodiment, the dielectric film 9 may be provided.

As described above, there is a method using a bonding layer to form the acoustic wave device of the first and second embodiments. The structure having such a bonding layer will be described by taking an elastic wave device according to the following third to eighth embodiments as an example.

7 is a schematic front sectional view of the acoustic wave device according to the third embodiment. In the acoustic wave device 11 of the third embodiment, the first silicon oxide film 12 is laminated on the support substrate 2. [ The high-sound-insulating film 3A is laminated on the first silicon oxide film 12. [ And a second silicon oxide film as a low-density acoustic film 4 is laminated on the high-pitched-in film 3A. The bass sound film 4 has a structure in which the bass sound film layer 4a and the bass sound film layer 4b are joined by a bonding layer 13. A piezoelectric film 5 is laminated on the bass sound insulation film 4. As described above, it is possible to obtain a sound insulation film having the first silicon oxide film 12 as the intermediate layer, the sound insulation film 4 having the low sound insulation film layers 4a and 4b and the bonding layer 13, The device 11 is similar to the acoustic wave device of the second embodiment.

In order to confine the elastic wave to the portion where the piezoelectric film 5 and the low sound insulating film 4 are laminated in the acoustic wave device 11, the thickness of the high sound attenuation film 3A is preferably as thick as possible. Therefore, the film thickness of the high-sound-quality film is preferably 0.5 times or more, and more preferably 1.5 times or more of? When the wavelength of the surface acoustic wave is?. The bonding layer 13 is a portion formed by metal diffusion bonding, as apparent from the manufacturing method described later, and is made of Ti oxide in the present embodiment.

Further, other metals may be used instead of Ti. Examples of such metals include Al and the like. The bonding layer 13 may be formed of a metal such as Ti or Al instead of a metal oxide. Preferably, however, a metal oxide or a metal nitride is preferable because electrical insulation can be achieved. In particular, an oxide or nitride of Ti is preferable because of high bonding strength.

In the acoustic wave device 11 of the present embodiment, since the low sound film 4 is laminated on the high sound film 3A and the piezoelectric film 5 is laminated on the low sound film 4, The Q value can be increased like the elastic wave device. Incidentally, in this embodiment, since the bonding layer 13 by metal diffusion is located in the low-sound-performance film 4, warpage at the wafer stage of the mother is hard to occur at the time of production. Therefore, even in the finally obtained acoustic wave device 11, it is difficult for the piezoelectric film 5 to be bent. Therefore, deterioration of characteristics is unlikely to occur. Therefore, cracks in the piezoelectric film 5, the support substrate 2, and the like are less likely to occur during the wafer transporting process and the product transportation at the time of manufacture. This will be described in more detail by describing the following manufacturing method.

In the production of the acoustic wave device 11, the first silicon oxide film 12 and the high-sound-after-production film 3A are laminated on the support substrate 2. Thereafter, a second silicon oxide film is laminated on the high-tone after-mentioned film 3A to form the low-sound-after-production film 4, thereby obtaining a first laminate. Separately, a second laminate having an IDT electrode formed on one side of the piezoelectric film and a silicon oxide film formed on the opposite side is prepared.

Then, a Ti layer is laminated on each of the silicon oxide film surface of the first laminate and the silicon oxide film surface of the second laminate. Next, the Ti layers of the first and second laminated bodies are brought into contact with each other and bonded under heating. In this case, Ti on both sides bonded together diffuses. Therefore, the bonding layer 13 is formed by metal diffusion bonding. Further, oxygen is supplied to the Ti layer from the silicon oxide film side. Therefore, the bonding layer 13 is made of Ti oxide. Therefore, sufficient electrical insulation is provided and the first and second laminated bodies are firmly bonded.

The thus obtained laminate is cut in units of the respective acoustic wave devices (11). Thereby, the acoustic wave device 11 can be obtained.

In the present embodiment, since the bonding layer 13 is located in the low-sound-attenuating film 4, warpage is unlikely to occur at the stage of obtaining the laminate obtained by bonding the first and second laminated bodies.

The present inventors have found that when the acoustic wave device described in Patent Document 1 is bonded using metal diffusion bonding, the piezoelectric film is warped in the laminate obtained by bonding the first and second laminate members. Further, in the acoustic wave device obtained by cutting the laminate in which the warp occurs, ripples appear in electrical characteristics such as resonance characteristics. On the other hand, after the bonding, it is also possible to eliminate the warpage by press molding under heating. However, the deterioration of the electrical characteristics was not recovered even if the processing for eliminating this warp was performed. Therefore, it is considered that a micro crack or the like occurs in the piezoelectric film due to the warping.

As a result of further study of the warpage, the inventors of the present invention have found that if the constitution of the first and second laminated bodies is selected such that the bonding layer 13 is provided in the low sound clearance film 4 as in the present embodiment, I found something that could be suppressed.

In Patent Document 1, a laminated structure composed of a piezoelectric film, a low-sound-insulating film and a high-sound-attenuating film, and a laminated structure composed of a medium layer and a supporting substrate are bonded. Therefore, a large film stress was applied to the piezoelectric film before bonding. Therefore, there is a tendency that a relatively large warpage occurs in the piezoelectric film in the laminate step in which the first and second laminate members are bonded.

On the other hand, in the present embodiment, in the second laminate, since only the silicon oxide film is laminated on the piezoelectric film, a large film stress is not applied to the piezoelectric film. Therefore, even in the laminate obtained by the bonding, since the stress applied to the piezoelectric film 5 is small, deflection is unlikely to occur. Therefore, it is difficult to cause deterioration of the electrical characteristics as described above. Further, cracks are hard to occur. This point will be described based on concrete experimental examples.

As the elastic wave device 11, a one-port type elastic wave resonator was produced. In addition, the number of pairs of electrode fingers of the IDT electrode was 100 pairs, the crossing width of the electrode fingers was 20?, And the wavelength determined by the electrode finger pitch was 2.0 占 퐉. For the reflector, the number of the electrode fingers was set to 20. The IDT electrode 6 and the reflector are made of metal made of Al and have a thickness of 160 nm.

Fig. 8 shows the resonance characteristics of the embodiment of the third embodiment by a solid line. For the sake of comparison, an elastic wave device was produced in the same manner as in the embodiment of the above embodiment, except that the bonding layer 13 was provided in the first silicon oxide film 12. Resonance characteristics of this conventional acoustic wave device are shown by broken lines in Fig. As apparent from Fig. 8, in the conventional example, the ripple is shown between the resonance point and the half-resonance point. On the other hand, according to the embodiment, it can be seen that such a ripple does not appear between the resonance point and the half-resonance point. In addition, the waveform (waveform) at the resonance point is sharper than the conventional example, and the peak-to-valley ratio of the impedance characteristic is also increased.

As described above, the reason why the resonance characteristic of the embodiment is higher than the resonance characteristic of the conventional example is that micro cracks based on the above-mentioned warping are not generated.

9 is a schematic front cross-sectional view of an acoustic wave device according to a fourth embodiment of the present invention.

In the acoustic wave device 21 of the fourth embodiment, the first silicon oxide film 12, the high-sound-after-production film 3A, the low-sound-insulating film 4, the piezoelectric film 5, Electrodes 6 are stacked. In the acoustic wave device 21 of the fourth embodiment, the bonding layer 13 is present in the high-sound-after-production film 3A. That is, the high-sound-after-thickness film 3A has high sound-attenuation film layers 3A1 and 3A2, and the bonding layer 13 is formed between the high sound attenuation film layer 3A1 and the high sound attenuation film layer 3A2.

Also in this embodiment, a second laminate having a low-sound-attenuating film and a high-sound-attenuating film layer may be prepared on a piezoelectric film at the time of manufacturing. Therefore, the piezoelectric film is hardly warped. Therefore, as in the first embodiment, deterioration of electrical characteristics is hardly caused even in the acoustic wave device 21. Further, cracks of the piezoelectric film in the wafer stage and finally obtained acoustic wave device 21 are also hard to occur.

10 is a schematic front sectional view of an acoustic wave device according to a fifth embodiment of the present invention.

The acoustic wave device 31 of the fifth embodiment is provided with the first silicon oxide film 12, the high-tone inner film 3A, the second silicon oxide film 4B, the bonding layer 13, a third silicon oxide film 4A, a piezoelectric film 5, and an IDT electrode 6 are stacked in this order. Here, the second silicon oxide film 4B and the third silicon oxide film 4A are all low-sound-insulating films. In the present embodiment, the bonding layer 13 is located at the interface between the second silicon oxide film 4B as the low acoustic impedance film and the third silicon oxide film 4A.

Also in the present embodiment, a second laminate having a third silicon oxide film 4A may be prepared on the piezoelectric film at the time of manufacturing. Therefore, the piezoelectric film is hardly warped. Therefore, deterioration of the electrical characteristics of the elastic wave device 31 is also less likely to occur. In addition, cracks of the piezoelectric film in the wafer stage and finally obtained acoustic wave device 31 are also hard to occur.

11 is a schematic front sectional view of an acoustic wave device according to a sixth embodiment of the present invention.

In the acoustic wave device 41 of the sixth embodiment, the first silicon oxide film 12, the high-tone soundproof film 3A, the low-sound-insulating film 4, the piezoelectric film 5, and the IDT Electrodes 6 are stacked. The bonding layer 13 is located at the interface between the low sound permeability film 4 and the piezoelectric film 5.

Also in the present embodiment, a second laminate comprising IDT electrodes laminated on a piezoelectric film at the time of manufacturing may be prepared. Therefore, the piezoelectric film is hardly warped. Therefore, deterioration of the electrical characteristics is also hard to occur in the elastic wave device 41. Further, cracks of the piezoelectric film in the wafer stage and finally obtained acoustic wave device 41 are also hard to occur.

If the bonding layer 13 is provided at any position from the high sound attenuation film 3A to the interface between the low sound attenuation film 4 and the piezoelectric film 5 like the acoustic wave devices according to the third to sixth embodiments do.

12 is a schematic front sectional view of an acoustic wave device according to a seventh embodiment of the present invention.

In the acoustic wave device 51, the low-sound-performance film 4 is laminated on the high-sound-speed support substrate 3. A piezoelectric film 5 is laminated on the bass sound insulation film 4. An IDT electrode 6 is formed on the piezoelectric film 5. Although not particularly shown, a reflector is provided on both sides of the IDT electrode 6 in the elastic wave propagation direction, thereby forming a one-port type elastic wave resonator.

The bonding layer 13 is located in the low sound insulating film 4 made of silicon oxide. That is, the bonding layer 13 is provided at the interface between the first low-noise film layer 4a and the second low-noise film layer 4b. Therefore, at the time of manufacturing, it is sufficient to prepare a second laminated body in which the IDT electrode 6 and the first bass film layer 4a are laminated on the piezoelectric film 5. Therefore, a large film stress is hardly applied to the piezoelectric film 5 in the second laminate. Therefore, the piezoelectric film is hardly warped.

At the time of manufacturing, a metal layer such as Ti or Al is formed on the surface of the second laminate on which the low-noise film layer is exposed. Then, a first laminated body in which the low sound film layer is laminated on the mother high-speed support substrate is prepared. A metal layer of Ti or the like is formed on the low-sound film layer of the first laminate. Then, the first and second laminated bodies are brought into contact with each other and bonded together under heating. In this way, the bonding layer 13 can be formed in the same manner as the acoustic wave device 11 of the third embodiment.

Thereafter, the obtained laminate is cut off, and each acoustic wave device 51 is obtained.

Also in the present embodiment, since the bonding layer 13 is provided at the above-mentioned position, warpage is hardly generated in the piezoelectric film step at the time of manufacturing. Therefore, deterioration of the electrical characteristics is unlikely to occur. In addition, cracks and micro cracks are unlikely to occur in the piezoelectric film 5 at the time of carrying the second laminate step and the product.

13 is a schematic front sectional view of an acoustic wave device according to an eighth embodiment of the present invention. In the acoustic wave device 61, the bonding layer 13 is located at the interface between the piezoelectric film 5 and the low sound insulating film 4. In other respects, the acoustic wave device 61 is the same as the acoustic wave device 51.

Also in the elastic wave device 61, the bonding layer 13 is located near the piezoelectric film 5 side. Therefore, it is difficult for the piezoelectric film 5 to be warped in the second laminate step before bonding. Therefore, as in the elastic wave device 51 of the seventh embodiment, deterioration of the electrical characteristics is hardly caused. Further, since the piezoelectric film 5 is hardly warped in the manufacturing process, cracks and micro cracks are hard to occur. Further, since the piezoelectric film 5 is hardly warped even when the product is transported, cracks and micro cracks are unlikely to occur.

Another intermediate layer may be laminated between the high-sound-speed supporting substrate 3 and the low-sound-attenuating film 4, even in the structure using the high-sound speed supporting substrate 3 like the elastic wave devices 51 and 61. That is, the low sound attenuation film 4 may be indirectly laminated on the high-sound-speed supporting substrate 3. In either case, in the structure using the treble support substrate 3, the bonding layer 13 may be located either in the low sound insulation film 4 or at the interface between the piezoelectric film 5 and the low sound insulation film 4.

Next, the relationship between the film thickness of the low-rate film and the Q value will be described below.

In the acoustic wave device 51 according to the seventh embodiment shown in Fig. 12, various acoustic wave devices were manufactured by changing the film thickness of the first low-acoustic-rate film layer 4a. More specifically, a high-sound speed support substrate 3 made of Si was used. As the second bass film layer 4b, a SiO ₂ film having a thickness of 55 nm was used. As the bonding layer 13, a Ti film was used and the thickness was set to 0.5 nm. As the piezoelectric film 5, a 600 nm LiTaO ₃ film was used. The wavelength lambda determined by the electrode finger pitch in the IDT electrode was 2 mu m. The first bass film layer 4a in contact with the piezoelectric film 5 was formed of SiO ₂ as silicon oxide to make the film thickness different.

14 shows the relationship between the film thickness of the SiO ₂ film as the first bass film layer 4a and the Q value.

It can be seen that the Q value becomes higher as the thickness of the SiO ₂ film as the first bass sound film layer 4a becomes thicker. When the film thickness of the SiO ₂ film is 240 nm or more, that is, 0.12λ or more, a high Q value exceeding 1000 is obtained. When the film thickness of the SiO ₂ film is 440 nm or more, that is, 0.22λ or more, the fluctuation of the Q value becomes small and becomes almost constant. Therefore, it can be seen that the Q value can be further increased and the deviation can be made smaller by setting the thickness of the SiO ₂ film to 0.22 lambda or more. Thus, preferably, when the low-acoustic film layer in contact with the piezoelectric film 5 is formed of silicon oxide, it is preferable that the thickness of the SiO ₂ film is 0.12λ or more. More preferably, the thickness of the SiO ₂ film is preferably 0.22λ or more.

Also, it is preferable that the thickness of the SiO ₂ film as the first low-noise film layer 4a be ₂ ? Or less. Thereby, the film stress can be reduced.

Next, the relationship between the film thickness of the Ti layer of the bonding layer and the Q value will be described.

The acoustic wave device 31 of the fifth embodiment shown in Fig. 10 was manufactured by changing the film thickness of the Ti layer of the bonding layer 13 to be different from each other. More specifically, the high-sound-after-production film 3A is formed of Si. The bonding layer 13 was formed of a Ti layer and a Ti oxide layer. The bonding layer 13 was formed so that the Ti oxide layer was located on the side of the high-frequency inductor 3A and the Ti layer was located on the side of the low-sound-insulating film 4. [ The thickness of the Ti oxide layer was set to 50 nm. The bass film was formed of SiO ₂ and had a thickness of 700 nm. The piezoelectric film 5 was formed of LiTaO ₃ and had a thickness of 600 nm. And the wavelength lambda of the surface acoustic wave as the acoustic wave used by the acoustic wave device 31 is 2 mu m.

15 is a diagram showing the relationship between the film thickness of the Ti layer as the bonding layer and the Q value.

It can be seen that the Q value becomes larger as the Ti layer thickness of the bonding layer becomes smaller. Particularly, when the film thickness of the Ti layer is 2.0 nm or less, that is, 1 x 10 ^-3 ? Or less, a high Q value exceeding 1000 is obtained. When the film thickness of the Ti layer is 1.2 nm or less, that is, 0.6 x 10 < ^-3 > or less, the fluctuation of the Q value becomes small and becomes almost constant. Therefore, it can be seen that the Q value can be further increased and the deviation can be made smaller by setting the film thickness of the Ti layer of the bonding layer to 1.2 nm or less, or 0.6 x ^10-3 ? Or less. Thus, preferably, the film thickness of the Ti layer is 2.0 nm or less, and more preferably, the film thickness of the Ti layer is 1.2 nm or less.

The thickness of the Ti layer is preferably 0.4 nm or more. Thereby, the first laminate and the second laminate can be properly bonded.

16 is a configuration diagram of the high-frequency front end circuit 130. As shown in Fig. In the same figure, the components (the antenna element 102, the RF signal processing circuit (RFIC) 103, and the baseband signal processing circuit (BBIC) 104) connected to the high frequency front end circuit 130 The RF front-end circuit 130, the RF signal processing circuit 103 and the baseband signal processing circuit 104 constitute a communication device 140. The communication device 140 is also connected to the high- It may include a power source, a CPU, and a display.

The high frequency front end circuit 130 includes an antenna side switch 125, a quadruplexer 101, a reception side switch 113 and a transmission side switch 123, a low noise & And an amplifier circuit 124. The acoustic wave device 1 may be a quadruplexer 101 or at least one of the filters 111, 112, 121, and 122.

Side switch 113 is connected to the individual terminal 111A which is the receiving terminal of the quad-plexer 101 and to the two terminals which are individually connected to the individual terminal 121A and to the low noise and circuit 114 And is a switch circuit having a common terminal.

Side switch 123 is connected to the individual terminal 112A which is the transmitting terminal of the quad-plexer 101 and two select terminals individually connected to the individual terminal 122A and the common terminal connected to the power amplifier circuit 124, Lt; / RTI >

The reception side switch 113 and the transmission side switch 123 respectively connect a common terminal and a signal path corresponding to a predetermined band in accordance with a control signal from a control unit (not shown), and for example, And a single pole double throw (SPDT) type switch. The number of selection terminals connected to the common terminal is not limited to one and may be plural. That is, the high-frequency front end circuit 130 may correspond to carrier aggregation.

The low noise and circuit 114 amplifies a high frequency signal (a high frequency reception signal in this case) via the antenna element 102, the quadruplexer 101 and the reception side switch 113, To the receiving amplifier circuit.

The power amplifier circuit 124 amplifies the high frequency signal (here, a high frequency transmission signal) output from the RF signal processing circuit 103 and outputs the amplified signal to the antenna element 102 To the transmission amplification circuit.

The RF signal processing circuit 103 processes the high frequency reception signal input through the reception signal path from the antenna element 102 by down-conversion or the like, and outputs the generated reception signal to the baseband signal processing circuit 104. The RF signal processing circuit 103 performs signal processing on the transmission signal inputted from the baseband signal processing circuit 104 by up-conversion or the like and outputs the generated high-frequency transmission signal to the power amplifier circuit 124 Output. The RF signal processing circuit 103 is, for example, an RFIC. The signal processed by the baseband signal processing circuit 104 is used, for example, for image display as an image signal, or as a voice signal. Further, the high-frequency front end circuit 130 may include other circuit elements between the above-described respective components.

According to the high-frequency front-end circuit 130 and the communication device 140 configured as described above, the quadruplexer 101 is included, thereby suppressing the ripple in the pass band.

The high frequency front end circuit 130 may include a quadruplexer according to a modification of the quadruplexer 101 instead of the quadruplexer 101 described above.

(Other Embodiments)

As described above, the elastic wave device, the high-frequency front end circuit, and the communication device according to the embodiment of the present invention have been described with reference to the embodiments and modifications thereof. However, the present invention can be applied to any component And a modification obtained by carrying out various modifications devised by those skilled in the art without departing from the gist of the present invention with respect to the above embodiments and the high frequency front end circuit and the communication device according to the present invention Various built-in devices are also included in the present invention.

For example, in the above description, it is assumed that the acoustic wave device may be a quadruplexer or a filter. However, in the present invention, in addition to the quadruplexer, for example, a triplexer in which three filter antenna terminals are common, The present invention is also applicable to a multiplexer such as a hexaplexer in which a filter antenna terminal is common. The multiplexer may include two or more filters.

The multiplexer is not limited to the configuration including both the transmission filter and the reception filter, and may include only the transmission filter or only the reception filter.

INDUSTRIAL APPLICABILITY The present invention can be widely applied to a communication device such as a cellular phone as a filter, a multiplexer, a front-end circuit, and a communication device applicable to a multi-band system.

1: elastic wave device 2: support substrate
3: High-speed support substrate 3A:
3A1, 3A2: High sound film layer 4:
4a, 4b: low sound film layer 4A: third silicon oxide film
4B: Second silicon oxide film 5: Piezoelectric film
6: IDT electrodes 7 and 8: reflector
9: dielectric films 11, 21, 31, 41, 51, 61: elastic wave device
12: first silicon oxide film 13: bonding layer
101: quadruplexer 102: antenna element
103: RF signal processing circuit 104: Baseband signal processing circuit
111, 112, 121, 122: filters 111A, 112A, 121A, 122A:
113: receiving side switch 114: low noise amplifier circuit
123: transmitting side switch 124: power amplifier circuit
125: antenna side switch 130: high frequency front end circuit
140: communication device

Claims (18)

As an elastic wave device having a piezoelectric film,
A high sound velocity member having a high sound velocity of a bulk wave propagating above the acoustic wave propagating through the piezoelectric film,
A low sound-absorbing film laminated on the high sound-attenuating member and having a low sound velocity of a bulk wave propagating more than an acoustic wave sound propagating through the piezoelectric film;
The piezoelectric film laminated on the bass sound film,
And an IDT electrode formed on one surface of the piezoelectric film,
And the film thickness of the piezoelectric film is more than 1.5? And not more than 3.5? When the wavelength of the acoustic wave determined by the electrode finger period of the IDT electrode is?. The method according to claim 1,
Wherein the treble member is a treble support substrate. 3. The method of claim 2,
Further comprising a bonding layer provided at either one of positions from the high-sound-speed supporting substrate to the interface between the bass sound film and the piezoelectric film. The method of claim 3,
Wherein the bonding layer is present at an interface between the high-sound-speed supporting substrate and the low-sound-attenuating film, in the low-sound-insulating film, or at an interface between the low-sounding attenuating film and the piezoelectric film Characterized in that 5. The method according to any one of claims 2 to 4,
Wherein the high-sound-speed supporting substrate is a silicon substrate. The method according to claim 1,
Wherein the high sound velocity member is a high sound wave film provided on the support substrate. The method according to claim 6,
Further comprising a bonding layer provided at any one position from the high-pitched inner film to the interface between the bare sound film and the piezoelectric film. 8. The method of claim 7,
Wherein the bonding layer is present at any one of an interface between the high-sound-attenuating film and the low-sound-attenuating film, an interface between the low-sounding attenuation film and the piezoelectric film, Device. 9. The method according to any one of claims 3 to 5, 7, and 8,
Wherein the bonding layer comprises a metal oxide layer or a metal nitride layer. 10. The method according to any one of claims 3 to 5 and 7 to 9,
Wherein the bonding layer comprises a Ti layer, and the thickness of the Ti layer is 0.4 nm or more and 2.0 nm or less. 11. The method of claim 10,
Wherein the thickness of the Ti layer is 0.4 nm or more and 1.2 nm or less. 12. The method according to any one of claims 1 to 11,
Wherein the bass sound film is made of silicon oxide or a film containing silicon oxide as a main component. 13. The method according to any one of claims 1 to 12,
Wherein the piezoelectric film is made of LiTaO ₃ . The method according to claim 4 or 8,
Wherein the bare sound film is made of silicon oxide and the bonding layer is present in the bare sound film and the bare sound film is positioned on the piezoelectric film side of the bonding layer; Wherein the first sound-absorbing film layer has a second sound-absorbing film layer located on the side opposite to the piezoelectric film, and the wavelength of the acoustic wave used by the acoustic wave device is lambda, Device. 15. The method of claim 14,
Wherein a thickness of the first bass sound film layer is 0.22 lambda or more. 9. The method according to any one of claims 6 to 8,
Further comprising an intermediate layer disposed between the treble mechnism and the support substrate. An acoustic wave device according to any one of claims 1 to 16,
Wherein the high-frequency front end circuit includes a power amplifier. A high-frequency front end circuit according to claim 17,
An RF signal processing circuit,
And a base band signal processing circuit.

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